SDN is a new network technology which emerges in recent years and the main features thereof are control and forwarding separation, network opening and programmability, and software and hardware separation. Due to the SDN, traditional communication network devices are liberated from dedicated hardware binding, and develop towards a direction of general-purpose hardware-based platform plus customized software, and realize network function virtualization, network management simplification and network deployment automation through open programmable interfaces. Therefore, as compared with the traditional network function realization and engineering implementation, the device cost, the labor cost and the deployment time are greatly reduced. As divided according to architecture hierarchies, SDN is basically divided into three layers from top to bottom, i.e., an application layer, a control layer and a data layer.
At present, the industry is performing or has already performed a great amount of standardization work on the control layer and the data layer. However, with respect to the application layer and the components inside the application layer, especially on how to integrate, manage and control applications and combine and merge with other existing applications and the like, the discussion is fewer and the program is relatively slow. That causes SDN has deficiency of capacities in aspects, such as, of usability, openness, programmability, manageability, operability, and compatibility and interconnection with existing applications and the like, which is adverse to the healthy development of SDN industry. Particularly the SDN has congenital handicaps in aspects, such as, of how to rapidly establish SDN developer communities and attract a great amount of SDN application developers to be concentrated on the solving of hotspot application problems, and migrating major applications in existing networks towards SDN technology, and the like.
Regardless of the Open Networking Foundation (ONF) standard organization or the Open Daylight (ODL) (SDN controller open-source organization), the application layer of SDN defined currently is mainly positioned to provide highly abstract functions, such as network application and network service orchestration. SDN application layer may perform network resource application and service orchestration according to user application requests, i.e., the SDN application layer upwards provides Application Programming Interface (API) calling (arctic interface) for external users through a Representation State Transfer (REST) mode and realizes customized application functions for external customers to realize virtualized network application functions; and the SDN application layer downwards provides network API interface calling (northbound interface) for SDN controllers through the REST mode and applies to the SDN control layer for resources to realize virtualized network service functions.
To view from the SDN application layer, current technical research and discussion and standardization work related thereto are mostly focused on the aspect of northbound interface between the SDN application layer and the SDN control layer. However, in actual application of SDN, services outwards provided by SDN are realized mainly through the interface (i.e., the arctic interface, also called as application interface) between the SDN application layer and the external upper application and the orchestration function inside the SDN application layer. Function demands related to the arctic interface and function demands related to orchestration have not been fully explored, and upper services related to the arctic interface and L4-L7 services using the northbound interface either are not discussed or are still under research and discussion at an early stage (e.g., service chain application); and particularly, the research and discussion about how to construct existing network services based on SDN has not been started. Therefore, those obstruct the integration of SDN applications and other existing applications to a certain extent and thereby influence the development of SDN application and SDN itself.
Further, for existing applications (for example CDN service, Over The Top (OTT) service and various video media services and so on) in the industry, with respect to the problem of how to satisfy the continuously increasing demands of terminal customers for service quality and the demand for continuous decrease of overall operation and maintenance costs by virtual of SDN architecture through open network programmable interfaces by better using high-efficiency, high-performance and high-cost-performance virtual network functions provided by bottom bearer networks, it is still at a very early initial discussion stage at present, and no clear solutions are provided, and this will restrict the pace of migrating the existing services towards SDN.
Relative to SDN, CDN is a comparatively mature technology, and is used for providing distribution and acceleration of media contents, such as web pages and videos and so on, for the Internet or telegraphy private networks. The major features of the CDN include: performing multi-level caching on media contents and providing proximity services for users to provide better experience quality for users.
Functions of CDN mainly include two parts, i.e., content distribution and content delivery (also called as media delivery), and basic functions include content distribution/delivery, scheduling/control, storage/cache, media service and the like. At present, international standard organizations, such as the International Telecommunication Union Telecommunication Standardization Sector (ITU-T), the European Telecommunication Standards Institute (ETSI), the 3rd Generation Partnership Project (3GPP) and the Internet Engineering Task Force (IETF) and the like, and industrial standard organizations, such as China Communications Standards Association (CCSA) and the like, all have related definition and standard specifications of CDN, which is used for bearing services, such as Internet Protocol Television (IPTV), Community Antenna Television (CATV), Over The Top Television (OTTTV) and mobile stream media and the like. At present, in CDN solutions limited for a reason that bottom bearer networks are not open, CDN used as a service network must exist as a superimposed layer and depend on the capability of a bottom-layer bearer network. In addition, servers, storage/cache servers and media servers required by the CDN solution all use dedicated hardware (such as blade servers/servers with an Advanced Telecom Computing Architecture (ATCA) or the like), and the dependence on hardware architecture is very high and there is no universality. Besides, since the network performance demand involved in the CDN is comparatively high (e.g., network bandwidth, delay and jitter and the like), great complexity is brought on network capacity expansion and management aspects, such as of address planning, device configuration, node deployment, service fulfillment and software upgrade and the like. For example, with the rapid development of services, such as IPTE, CATV, OTT and mobile stream media and the like, CDN is gradually decoupled from services to become a pipe for content transmission integrating and bearing various services, resulting in more and more CDN deployment nodes, larger and larger network scale, more and more complex management of CDN content routing, and more and more difficult management of multiple service providers/content providers (CPs/SPs), and service configuration.
Aiming at the above-mentioned problems existing in current CDN related technical solutions, in consideration of the technical development trend of CDN, it is urgent to discuss about the integration of CDN and SDN and how to introduce SDN technology into CDN solutions to effectively solve the problems confronted by CDN in aspects, such as of closeness of bearer networks, specificity of hardware and complexity of management, and to further improve the openness, cost performance and usability of CDN and reduce overall operation and maintenance costs of CDN.